Electrochemiluminescence evaluation for carbohydrate antigen 15-3 based on the dual-amplification of ferrocene derivative and Pt/BSA core/shell nanospheres

Electrochemiluminescence resonance energy transfer detection of HBsAg based on Co doped 3D porous luminol-based conjugates and quencher UiO-66-NH2@Au

An electrochemiluminescence (ECL) biosensor based on ECL resonance energy transfer (ECL-RET) was designed to sensitively detect hepatitis B virus surface antigen (HBsAg). In this ECL-RET system, luminol was employed as ECL donor, and gold nanoparticles functionalized zirconium organoskeleton (UiO-66-NH2@Au) was prepared and served as ECL acceptor. The UiO-66-NH2@Au possessed an ultraviolet-visible (UV-vis) absorption between 400 nm and 500 nm, and the absorption spectra overlapped with the ECL spectrum of luminol. Furthermore, Graphene oxide-poly(aniline-luminol)-cobalt nanoparticles conjugates (GO-PALu-Co) was prepared to optimize the ECL behavior through the catalysis of Cobalt nanoparticles and served as a stable 3D porous film to load capture probe primary antibody (Ab1). Based on the ECL-RET biosensing method, the UiO-66-NH2@Au-labeled Ab2 and target HBsAg could pair with primary antibody Ab1 to form sandwich-type structure, and the ECL signal of GO-PALu-Co was quenched. Under optimized experimental conditions, the ECL-RET analytical method represented eminent analytical performance for HBsAg detection with a wide linear relationship from 2.2 × 10-13 to 2.2 × 10-5 mg/mL, and a detection limit of 9 × 10-14 mg/mL (S/N = 3), with spiked sample recoveries ranging from 97.27 % to 102.73 %. The constructed sensor has good stability, reproducibility, and specificity. It can be used to detect HBsAg in human serum and has the potential to be used for the sensitive detection of other disease biomarkers.

CTAB-Co-MOFs@AuPt NPs as signal probes for the electrochemical detection of carcinoembryonic antigen 15-3

A sensitive electrochemical strategy for carcinoembryonic antigen 15-3 (CA15-3) detection is reported using CTAB-Co-MOFs@AuPt NPs as signal probes. The electrochemical strategy was designed as follows: First, the graphene aerogel@gold nanoparticles (GA@Au NPs) nanocomposites were employed to modify the sensing surface for promoting electron transfer rate and primary antibody (Ab1) immobilization due to GA possesses a large specific surface area, eminent conductivity, and a 3D network structure. Cobalt metal-organic frameworks (CTAB-Co-MOFs) synthesized were then used as a carrier for AuPt NPs and secondary antibody (Ab2) immobilization (notes: labelled-Ab2). With sandwich immunoreaction, the labelled-Ab2 was captured on the surface of the GA@Au NPs nanocomposites. Finally, differential pulse voltammetry (DPV) was employed to register the electrochemical signal of the immunosensor at the potential of - 0.85 V (vs SCE) in phosphate buffer saline (PBS) containing 2.5 mM H2O2. It was verified that the electrochemical reduction signal from Co3+ to Co2+ was recorded. The AuPt NPs could catalyze the reaction of H2O2 oxidizing Co2+ to Co3+, resulting in the amplification of the electrochemical signal. Under the selected conditions, the immunosensor can detect CA15-3 in the range 10 µU/mL to 250 U/mL with a low detection limit of 1.1 µU/mL. In the designed strategy, the CTAB-Co-MOFs were not only employed as carriers for AuPt NPs, but also acted as signal probes. The CTAB-Co-MOFs were investigated including SEM, TEM, XPS, and XRD. The application ability of the immunosensor was evaluated using serum sample, demonstrating the immunosensor can be applied to clinic serum analysis.

A portable microfluidic device integrated with electrochemical sensing platform for detection of multiple binders in ancient wall paintings

The aging of the proteinaceous binders will cause the cultural relics to suffer from diseases such as flaking, cracks, and even peeling. Identifying the type of binders in a timely manner is conducive to restore diseased cultural relics. High-throughput and portable detection system are of great significance for researching cultural relic materials on the archaeological site. Therefore, in this work, a portable electrochemical microfluidic device for the simultaneous detection of casein, ovalbumin, and peach gum binders was developed. The proposed electrochemical immunosensor technology integrated with microfluidic device achieve the goals of miniaturization, portability and reagent-saving. For casein, ovalbumin and peach gum, excellent performance was obtained in terms of their limits of detection (LOD) at 0.237, 0.507, and 0.403 ng mL^-1 (S/N = 3), respectively. In addition, the microfluidic sensing platform exhibited acceptable anti-interference ability, stability, and storage capacity. In order to evaluate the practical application value, the proposed microfluidic sensing device was applied for detecting eight archaeological samples from different historic sites. This work demonstrates great potential for high-throughput, portable detection of cultural relic proteinaceous binder materials.

Hairpin oligosensor using SiQDs: Förster resonance energy transfer study and application for miRNA-21 detection

MicroRNAs are known to be tumor suppressors and promoters and can be used as cancer markers. In this work, a novel oligosensor was designed using Si quantum dots (SiQDs) for the detection of miRNAs. Five-nanometer SiQDs were synthesized, with a band gap of 2.8 eV, fluorescence lifetime of 4.56 μs (τ1/2 = 3.26 μs), quantum yield of 25%, fluorescence rate constant of 6.25 × 104, and non-radiative rate constant of 1.60 × 105 s-1. They showed excellent water dispersibility, good stability (with 95% confidence for 6-month storage) without photobleaching, and high biocompatibility, with an IC50 value of 292.2 μg/L. The SiQDs and Black Hole Quencher-1 (BHQ1) were conjugated to the 5' and 3' terminals of an oligomer, respectively. The resulting hairpin molecular beacon showed resonance energy transfer efficiency of 63%. A distance of 0.91 R (Förster distance) between SiQD and BHQ1 was obtained. In the presence of a stoichiometric amount of the complementary oligonucleotide (ΔGhybridization = -35.09 kcal mol-1), 98% of the fluorescence was recovered due to loop opening of the hairpin structure. The probe showed good selectivity toward miRNA-21, with a limit of detection of 14.9 fM. The oligosensor recoveries of miRNA-21 spiked in human serum and urine were 94-98% and 93-108%, respectively.

Integrating potential-resolved electrochemiluminescence with molecularly imprinting immunoassay for simultaneous detection of dual acute myocardial infarction markers

A novel potential-resolved molecularly imprinted electrochemical luminescence (ECL) immunosensor has been developed for the first time for the dual sensitive detection of markers of acute myocardial infarction (AMI): cardiac troponin I (cTnI) and myoglobin (Mb). In this work, cost-effective and robust molecularly imprinted polymer (MIP) as biomimetic antibody was used to construct the immunosensors through electropolymerization and elution to form polydopamine (PDA)-MIP modified electrode. In the presence of AMI biomarkers, two ECL probes including Ru(bpy)₃²⁺@ MOCs and MoS₂ QDs functionalized by cTnI antibody and Mb aptamer could be specifically captured respectively. And two potential distinct ECL signals will be generated in one potential scan. The intensity of ECL reflects the concentrations of cTnI and Mb. The two ECL probes were characterized with field emission scanning electron microscopy, X-ray diffraction, FT-IR spectrum and UV-Vis diffuse reflectance spectroscopy. The prepared sensor exhibited a wide linear range (0.05-10⁴ ng/mL) and a low detection limit (0.0184 ng/mL for cTnI and 0.0492 ng/mL for Mb). Additionally, the MIP-ECL sensor displayed excellent anti-interference, sensitivity and stability to detect cTnI and Mb. Therefore, it will be conducive to accelerate more precise and credible early diagnosis for AMI.

Rationally constructed ZnCdS-HDCs@In2S3-HNRs double-hollow heterojunction with promoted light capture capability for photoelectrochemical biosensing

The construction of novel heterojunction is regarded as an operative scheme to promote the transport of photogenerated carriers and reduce electron-hole pair recombination to enhance the photoelectrochemical (PEC) performances. Herein, ZnCdS hollow dodecahedral nanocages (ZnCdS-HDCs) and In₂S₃ hollow nanorods (In₂S₃-HNRs), which were derived from two different of metal-organic frameworks (MOFs) by solvothermal sulfidation method and were constructed an original double-hollow heterostructure ZnCdS-HDCs@In₂S₃-HNRs. The intrinsic mechanism of In₂S₃-HNRs benefiting from unique morphology to boost the photochemical properties under visible light irradiation was illustrated. Meanwhile, the mechanism of the novel type II heterojunction with staggered matching levels was revealed, which could effectively restrict electron-hole pair reassociation separation, and accelerated charge separation and transfer. Therefore, based on the excellent PEC performance of ZnCdS- HDCs@In₂S₃-HNRs double-hollow heterostructure, a signal-off PEC biosensor platform without labeled was constructed for the detection of CA15-3, which manifested acceptable specificity, reproducibility and stability. Additionally, the expected PEC biosensors showed a linear response range from 1.0 × 10^-5 to 10 U·mL^-1 in addition to an ultralow detection limit of 3.78 × 10^-6 U·mL^-1. This study innovatively constructed and prepared a new double-hollow heterojunction material with superior PEC nature for the application of PEC biosensing, which exhibits a broad application prospect.

Electrochemiluminescent immunoassay for the determination of CA15-3 and CA72-4 using graphene oxide nanocomposite modified with CdSe quantum dots and Ru(bpy)3 complex

A novel immunoassay is introduced based on co-reactant enhancing strategy for the electrochemiluminescent (ECL) determination of CA15-3 and CA72-4 tumor markers in real samples. For the preparation of the signaling probe, CA15-3 and CA72-4 antibodies first were labeled using Ru(bpy)₃²⁺-N-hydroxysuccinimide ester (Ru(bpy)₃²⁺-NHS) and conjugated with L-cysteine capped cadmium selenide (CdSe) quantum dots. Finally, it was cross-linked with chitosan-grafted graphene oxide (GO@CS) nanocomposite. The capture probe was constructed by deposition of multi-walled carbon nanotubes (MWCNT) at the surface of dual-working gold screen-printed electrodes (MWCNT-dwSPE) and covalent attachment of capture CA15-3 and CA72-4 antibodies to MWCNT-dwSPE. ECL signals were recorded by applying cyclic potential ranging from 0.3 to 1.1 V (vs. pseudo-reference Ag/AgCl) at the scan rate of 100 mV.s^-1. This immunoassay was used for determination of CA15-3 and CA72-4 in real samples the detection limits of 9.2 μU.ml^-1 and 89 μU.ml^-1 within linear ranges of 10 μU.ml^-1-500 U.ml^-1 and 100 μU.ml^-1-150 U.ml^-1, respectively. This immunoassay also showed acceptable accuracy with recoveries in the range 96.5-108 % and high reproducibility with RSD of 3.1 and 4.9.

A label-free electrochemical immnunosensor based on signal magnification of oxygen reduction reaction catalyzed by uniform PtCo nanodendrites for highly sensitive detection of carbohydrate antigen 15-3

Developing a highly sensitive immunoassay for tumor biomarkers is particularly important in bioanalysis and early disease diagnosis. In this work, a simple one-pot solvothermal method was developed for controllable synthesis of well-dispersed PtCo alloyed nanodendrites (PtCo NDs) by using l-carnosine as the co-structure-directing agent. The PtCo NDs had a large specific surface area and provided abundant active sites available for electrocatalytic oxygen reduction reaction (ORR). Based on the highly enhanced currents of the ORR, a novel label-free electrochemical immunosensor was fabricated for highly sensitive assay of carbohydrate antigen 15-3 (CA15-3). The sensor showed a wide linear range of 0.1-200 U mL^-1 and a low limit of detection (LOD) down to 0.0114 U mL^-1 (S/N = 3), in turn exploring its application to diluted human serum samples with satisfactory results. This study provides a feasible platform for monitoring other tumor markers in clinical diagnosis.

Ultrasensitive detection of cyclin D1 by a self-enhanced ECL immunosensor based on Bi2S3 quantum dots

Bismuth sulfide quantum dots (Bi₂S₃ QDs), which have excellent optical and thermoelectric properties, represent a green and non-toxic semiconductor material that has been widely used in catalysis and photoelectric conversion devices. At present, research on this material has gradually expanded into the biological field. Herein, the biomineralization method mediated by bovine serum albumin (BSA) was utilized to synthesize Bi₂S₃ QDs with monodispersity, excellent colloidal stability, and good biocompatibility. This is the first study on the electrochemiluminescence (ECL) characteristics of Bi₂S₃ QDs and related ECL mechanisms in detail. In addition, on the basis of Bi₂S₃ QDs, an ECL immunosensor was used for the ultrasensitive measurement of cyclin D1 (CCND1). The composite material, namely Au@Cu-Bi₂S₃ QDs was used as a high-sensitivity ECL probe, in which AuNPs were connected with Bi₂S₃ QDs through a copper(ii) ion bridge. PDA-AgNPs made of dopamine (DA) and silver nanoparticles (AgNPs) were utilized as a carrier for fixing the primary antibody (Ab₁), ultimately presenting a relatively wide detection range of 10 fg mL^-1-1 μg mL^-1. Moreover, quite a low detection limit (6.34 fg mL^-1) was also obtained for an assay of CCND1. Results indicated that the immunosensor can provide a potential platform with fine stability and creditable reproducibility for clinical diagnosis.

Electrochemiluminescence resonance energy transfer between luminol and black phosphorus nanosheets for the detection of trypsin via the “off–on–off” switch mode

In this work, the electrochemiluminescence behavior of a luminol–H₂O₂ system was studied on a black phosphorus nanosheet modified electrode.

Sensitive and Simple Competitive Biomimetic Nanozyme-Linked Immunosorbent Assay for Colorimetric and Surface-Enhanced Raman Scattering Sensing of Triazophos

The biomimetic enzyme-linked immunosorbent assay (BELISA) is widely used for detection of small-molecule compounds as a result of low cost and reagent stability of molecularly imprinted polymers (MIPs). However, enzyme labels used in BELISA still suffer some drawbacks, such as high production cost and limited stability. To overcome the drawbacks, a biomimetic nanozyme-linked immunosorbent assay (BNLISA) based on MIPs and nanozyme labels was first proposed. For nanozyme labels, platinum nanoparticles (PtNPs) acted as peroxidase by catalyzing the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into an ideal surface-enhanced Raman scattering (SERS) marker. Blue TMB²⁺ and bovine serum albumin (BSA)-hapten showed superior selectivity when competing with targets for binding sites on MIPs, named the Pt@BSA-hapten probe. The BNLISA method was employed to detect triazophos with a limit of detection of 1 ng mL^-1 via colorimetric and SERS methods. Replacing traditional enzymes with nanozymes for combination with MIPs may bring about a new prospect for other compound analyses.

A Novel Carbon Quantum Dots Signal Amplification Strategy Coupled with Sandwich Electrochemiluminescence Immunosensor for the Detection of CA15-3 in Human Serum

A sensitive sandwich electrochemiluminescence immunosensor was established by employing graphene oxide-PEI-carbon quantum dots (CQDs)-Au nanohybrid as probe to measure carbohydrate antigen 15-3 (CA15-3), a breast cancer biomarker. In this work, nanocomposites of Ag nanoparticles and polydopamine (AgNPs-PDA) were synthesized by redox reaction between dopamine and Ag⁺. The nanocomposite with high surface area can provide an efficient substrate for immobilizing initial antibody (Ab1). Carbon quantum dots (CQDs) are fixed on polyethylenimine-functionalized graphene oxide (PEI-GO) by amide bonds. Au nanoparticles are modified on CQDs-decorated PEI-GO substrates. The secondary antibody (Ab2) was immobilized by AuNPs/CQDs-PEI-GO composite. CQDs can be assembled onto the surface of an electrode by incorporation of CA15-3 with Ab1 and Ab2. Under the synergistic action of AgNPs, polydopamine, AuNPs, and PEI-GO, the ECL signal of CQDs is greatly amplified as an excellent conductive material to facilitate electron transfer rate and further increase electrochemical detection capability. Under optimal conditions, the fabricated immunosensor showed a linear concentration range from 0.005 to 500 U mL^-1, with a detection limit of 0.0017 U mL^-1 (signal-to-noise ratio of 3) for CA15-3. The designed ECL immunosensor displayed receivable accuracy, excellent stability, and high specificity. The results of the detection of human serum samples are satisfactory, revealing that the method offers a potential application for the clinical diagnosis of tumor markers.

An enzyme-free electrochemiluminescence biosensor for ultrasensitive assay of Group B Streptococci based on self-enhanced luminol complex functionalized CuMn-CeO2 nanospheres

Herein, a novel and pragmatic electrochemiluminescence (ECL) biosensing method was developed for ultrasensitive and specific detection of Group B Streptococci (GBS) by combining self-enhanced luminol complex functionalized CuMn-CeO₂ (CuMn-CeO₂-PEI-luminol) with MNAzyme-mediated target-recycling amplification. First, the efficient self-enhanced PEI-luminol luminophore was prepared by combining PEI co-reactant with luminol in one molecular, which shortened electron transfer distance and enhanced ECL signal. And CuMn-CeO₂ was applied to load a large number of PEI-luminol and strengthen luminous efficiency of luminol by the high catalytic activity toward H₂O₂ oxidation. Then, target-driven MNAzyme system was used to realize the circulation of GBS nucleic acid sequence, producing plentiful triggers to initiate the hybridization reaction on the surface of electrode. The developed enzyme-free ECL biosensor showed ultra-sensitivity for target DNA detection with detection limits of 68 aM (synthetic DNA) and 5 × 10² CFU mL^-1 (genomic DNA extracted from GBS strain). More importantly, this biosensor was successfully applied for detection of genomic DNA of GBS extracted from clinical vaginal/anal swabs as low as 320 copies. Thus, this proposed strategy might be an pragmatic ECL platform for ultrasensitive and specific detection of GBS in clinical vaginal/anal swabs.

Amplified photoelectrochemical immunoassay for the tumor marker carbohydrate antigen 724 based on dye sensitization of the semiconductor composite C3N4-MoS2

The authors describe an amplified photoelectrochemical immunoassay for the tumor marker carbohydrate antigen 724 (CA724). The method employs a C₃N₄-MoS₂ semiconductor as the photoelectric conversion layer. The nanocomposite was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, and UV-vis diffuse reflectometry. The dye eosin Y was encapsulated into CaCO₃ nanospheres which then were used as labels for antibody against CA724. In addition, Fe₃O₄ nanospheres were employed as magnetic platform for constructing photoelectrochemical sandwich immunoassay. The CaCO₃ nanospheres can be dissolved with aid of ethylene diamine tetraacetic acid (EDTA) and the carried eosin Y in CaCO₃ is released. The released dyes sensitizes the C₃N₄-MoS₂ semiconductor, which induces photocurrent amplification. Under optimal conditions and at a typical working voltage of 0 V (vs. SCE), the photocurrent increases linearly in the range of 0.05 mU mL^-1 to 500 mU mL^-1 of CA724, with a 0.02 mU mL^-1 detection limit. Graphical abstract The C₃N₄-MoS₂ complex, with high efficiency of electron transport, was synthesized to construct a photoelectrochemical analytical platform. A sandwich-type immunoassay was established on the surface of magnetic beads. Carbohydrate antigen 724 in sample was detected sensitively by using sensitization of released eosin Y as signal amplifiery.